Studies of small areas, such as communities or counties, are an important tool of epidemiologists, who are interested in studying distributions of diseases in populations. Many studies of this type have been reported in the scientific literature. An assessment of techniques of analysis frequently used in these studies was initiated to determine their adequacy for use in the NINCDS survey of major neurological disorders in Copian County, Mississippi (Y01-NS-70031, N01-NS-7-2357).